1. Field of the Invention
The present invention relates to a tear structure of an air bag door and more particularly to a tear structure comprising two sheets of door panels which are formed integrally with the base of the upholstery member of a vehicle and open to both sides when an air bag system is actuated and two sheets of movable reinforcing panels which are fitted to a bracket disposed on the back side of the base in such a manner as being openable to both sides and fixed correspondingly to the door panels, wherein when an air bag starting to expand simultaneously with the operation of the air bag system presses the movable reinforcing panels from the inside, there occurs the rupture of tear seams formed along the center line where the two sheets of adjoining door panels meet and along the outer edge lines thereof to timely open the door panels toward a passenger""s chamber.
2. Description of the Related Art
In recent years, almost all passenger cars are normally equipped with air bag systems for car drivers"" and front passengers"" seats in order to protect on-board persons from impacts due to collisions and the like. The air bag system for the car driver""s seat is usually installed in a horn pad portion in the center of a steering wheel. However, as shown in FIGS. 10 and 11, for example, the air bag system for the front passenger""s seat is installed in such a way that it is housed inside an instrument panel 10 as a vehicle upholstery member that is located in front of the passenger""s seat and incorporated in the forepart of a passenger""s chamber 45. Therefore, an air bag door 12 to be opened and displaced toward the passenger""s chamber 45 is separately mounted or integrally formed in a region corresponding to the air bag system 20 for the passenger""s seat in the panel base 11 of the instrument panel 10. When the door 12 is released from the panel base 11, an open partition toward the passenger""s chamber 45 is formed. More specifically, when the air bag system 20 operates on sensing an impact due to a collision, an inflated air bag 21 forces the air bag door 12 to open from the inside and develops into the passenger""s chamber 45 via the open partition.
Heretofore, it has been a common practice that the air bag door 12 is separately formed from the panel base 11 of the instrument panel 10 and mounted therein. In recent years, however, the number of air bag doors 12 integrally formed with the respective panel bases 11 is on the increase. In other words, the air bag door 12 usually forms a design surface as part of the panel base 11 as shown in FIGS. 10 and 11 and when the air bag door 12 receives the pressing force from the inflating air bag 21 after the air bag system 20 operates, rupture occurs along tear seams 15 and 16 that are provided in the panel base 11 beforehand, so that the tear seams 15 and 16 are separated from the panel base 11 and allowed to open. With respect to the form of the air bag door 12, there are, for example, a one-side opening type having one door panel portion, a both-side opening type (as shown in the drawings) having two sheets of door panels and so forth. In any one of the types, however, an important matter is not to hinder the smooth development of the air bag 21 expected to take approximately {fraction (1/100)} second from beginning to completion of its inflation.
As the panel base 11 integrally forming the air bag door 12 is generally a synthetic resin molded material of polypropylene or the like, the panel base 11 itself including the air bag door 12 may be damaged by an impact resulting from receiving strong pressing force from the air bag 21 particularly at low temperatures (below zero) and there is immanent possibility of developing problems in view of its strength and safety. Consequently, measures to increase the strength by fitting a metal reinforcing member 25, for example, by caulking to the periphery of the air bag door 12 on the back side of the panel base 11 in order to prevent the air bag door 12 from being damaged and scattered off.
On condition that the both-side opening type air bag door 12 having the two sheets of door panels 13 and 14 is employed, the metal reinforcing member 25 includes, as shown in FIGS. 11, 12 and 13A, a rectangular frame-like fixing bracket 26 fixed in such a manner as to surround the edged tear seam 16 formed along the outer edge lines of the door panels 13 and 14 formed on the panel base 11, and movable brackets 27 and 27 mounted face-to-face on the inner side of the opening of the fixing bracket 26. The fixing bracket 26 includes a tubular portion 28 for retaining and holding the air bag system 20, and a retaining plate portion 29 that is integrally molded to the tubular portion 28 and fitted by caulking to the back side of panel base 11. Further, the movable brackets 27 and 27 correspond to the respective door panels 13 and 14 of the air bag door 12, each of the movable brackets 27 and 27 including fixing support panels 30 fitted by welding or machine screws to the tubular portion 28 of the fixing bracket 26, and movable reinforcing panels 31 that are pivotally joined to the respective fixing support panels 30 and also joined by caulking to the undersides of the corresponding door panels 13 and 14. With the panel base 11 for mounting the metal reinforcing member 25, the door panels 13 and 14 and the outer peripheral portions of the air bag door 12 are reinforced thereby so that the panel base 11 may become strong enough to sufficiently resist the strong pressing force generated by the inflation of the air bag 21.
Incidentally, the conventional idea about the air bag door 12 was to attempt to increase the strength of the air bag door 12 itself by means of the metal reinforcing member 25, and the chief aim of this was to avoid the damage caused by the strong pressing force of the air bag 21. Therefore, the movable reinforcing panel 31 of the movable bracket 27 fixed to the underside of each of the door panels 13 and 14 has I-, L- or T-shaped reinforcing recessed portions 33 in proper places as shown in FIG. 12 whereby to prevent the deformation of each of the door panels 13 and 14 of the air bag door 12 by increasing the strength of the movable reinforcing panel 31 itself against bending, deflection and twisting as shown in FIG. 12. In this case, as the air bag 21 to be inflated through the operation of the air bag system 20 inflates in a spherical shape with the center of its upper face being inflated as shown in FIG. 10, the strongest pressing force is applied to the vicinity of the center (substantially central region of the central tear seam 15) between the opposed edge portions of the movable reinforcing panels 31 and 31 fixed to the underside of the air bag door 12. However, because the movable reinforcing panels 31 and 31 are almost free from deformation against the pressing force of the air bag 21, substantially equal push-up force is applied to the whole surface of the corresponding door panels 13 and 14.
When the air bag 21 starts inflating at the initial pressing stage, both the door panels 13 and 14 of the air bag door 12 are pushed up substantially without being bent-deformed, and the central tear seam 15 formed along the center line between the adjoining door panels 13 and 14 and the edged tear seam 16 formed along the outer edge lines are totally and simultaneously ruptured (sheared), so that partial rupture hardly occurs. As is well known, however, the force needed to rupture the tear seams 15 and 16 totally and simultaneously is far greater than what is needed to partially rupture part of the tear seams 15 and 16 first and then to make the rupture extend to the whole. Therefore, because no rupture of the tear seams 15 and 16 occurs unless the internal pressure of the air bag 21 rises with the proper passage of time and unless an increase in the pressing force follows, the completion of the total rupture will be delayed even though the delay happens in a moment. The delay in rupturing the tear seams 15 and 16 at this time results in delaying the opening and displacement of the air bag door 12, which means that as the smooth inflation of the air bag 21 is obstructed, the overall development of the air bag 21 toward the passenger""s chamber 45 is also delayed. In case where the development of the air bag 21 does not progress properly, the air bag system does not function as a safety system and poses an extremely serious problem in that it is unable to ensure safety of the passenger.
The internal pressure of the air bag 21 has so considerably risen at the beginning of the rupture of the tear seams 15 and 16, that, greater pressing force than usual is applied to the air bag door 12, and the periphery of the air bag door 12 (the panel base 11) may be damaged by the rupture thereof without suitable rupture propagation along the tear seams 15 and 16. In such a case as that, any part without being fixed to the metal reinforcing member 25 will be damaged and in case where the part is reduced to broken pieces, a new problem of causing the broken pieces to scatter behind the passenger""s chamber and to collide with the passenger will also be pointed out. Further, there is the possibility that the air bag door 12 itself may be blown off as the air bag door 12 is abruptly opened and displaced.
In addition, as shown in FIG. 13A, the movable brackets 27 and 27 in the conventional metal reinforcing member 25 is formed by only bending a movable reinforcing panel 31 at a bending fulcrum 38 with respect to the fixing support panel 30 and when the air bag 21 presses the movable reinforcing panel 31 upward, the movable reinforcing panel 31 is pivotally displaced round the bending fulcrum 38. As shown in FIG. 13B, however, in the air bag door 12 like this, the end portion 14a (13a) on the outer edge line side of the door panel 14 (13) fitted by caulking to the movable reinforcing panel 31 interferes with the panel base 11 and the inherent drawback is that as the opening and displacement of the door panel 14 (13) is restricted, the smooth overall development of the air bag 21 toward the passenger""s chamber 45 is not ensured. When the air bag 21 forcibly presses the movable reinforcing panel 31 upward, moreover, the interference of the end portion 14a (13a) causes the door panel 14 (13) to be pushed in the direction of an arrow in FIG. 13B. Consequently, it is feared that the door panel 14 (13) may be isolated from the movable reinforcing panel 31 and scattered.
In order to avoid the inconvenience above, there has been proposed an arrangement of coupling the movable reinforcing panel 31 to each fixing support panel 30 with an extendable deformable coupling member, a slidable coupling member or the like. When the air bag 21 presses the movable reinforcing panel 31 upward in such an improved air bag door, the edged tear seam 16 first ruptures simultaneously with the extension and deformation or sliding displacement of the coupling members to move the door panels 13 and 14 upward from the panel base 11. Then the central tear seam 15 ruptures whereby to open and displace each of the door panels 13 and 14. With the air bag door in the above form, the end portion 14a (13a) of the door panel 14 (13) fitted by caulking to the movable reinforcing panel 31 is prevented from interfering with the panel base 11 and this makes possible the opening and displacement of the door panel 14 (13). Thus, the smooth overall development of the air bag 21 toward the passenger""s chamber 45 is never obstructed because the door panel 14 (13) is excessively opened.
Although the upward movement of the door panels 13 and 14 results in appropriately preventing the end portions 13a and 14a of the respective door panels 13 and 14 from interfering with the panel base 11 as long as the improved air bag door above is concerned, each of the door panels 13 and 14 pressed upward by the air bag 21 is opened and displaced with great force and there is developed a new problem of making the door panels 13 and 14 collide violently with the outer surface of the panel base 11. In other words, with the improved air bag door, the impact caused when the door panels 13 and 14 collide with the panel base 11 grows greater than before as the opening and displacement of the door panels 13 and 14 become entirely uncontrolled. Therefore, there inherently exists the possibility of rather increasing a degree of damaging the door panels 13 and 14 as well as the panel base 11.
An object of the present invention is to properly solve the foregoing problems and to provide a tear structure of an air bag door for allowing door panels to be smoothly opened and displaced and also allowing an air bag to be smoothly and totally developed by deformably forming movable reinforcing panels fixed to the undersides of the respective door panels so as to allow the partial deformation of the door panels when the door panels receive the pressing force of the air bag, and letting the total rupture of tear seams progress after the tear seams corresponding to the door panels are caused to partially rupture.
Another object of the present invention is to provide an air bag door opening structure for use in preventing door panels and a panel base from being damaged when the door panels are ruptured, separated and properly driven upward from the panel base while an air bag is inflating after an air bag system is actuated in order to open and displace the door panels by arranging each of the door panels pressed upward by the air bag so that the door panels may be stopped from opening before the door panels collide with the panel base.
In order to accomplish the object above, according to an aspect of the invention, there is provided a tear structure of an air bag door, wherein an air bag door comprises two sheets of door panels which are integrally formed with the panel base of a vehicle upholstery member and opened to both sides when an air bag system is actuated, and two sheets of movable reinforcing panels which are fitted to a bracket disposed on the back side of the panel base in such a manner as openable to both sides and fixed to the back sides of the corresponding door panels, wherein when an air bag starting to inflate after the air bag system is actuated presses the movable reinforcing panels upward from the inside, tear seams formed along a center line between the two sheets of adjoining door panels and along their outer edge lines rupture to open and displace the door panels toward a passenger chamber whereby to totally develop the air bag toward the passenger chamber, is characterized in that:
the movable reinforcing panels are respectively formed with a plurality of serially-combined panel members disposed along bending lines of opening the door panels and that
when the air bag starting to inflate after the operation of the air bag system presses any one of the panel members upward in the movable reinforcing panels, regions corresponding to the panel members of the door panels are deformed outward and the tear seams situated closest to the deformed regions are caused to partially rupture in order to prompt the total rupture of these tear seams.
According to another aspect of the invention, there is provided an air bag door opening structure, wherein an air bag door comprises two sheets of door panels which are integrally formed with the panel base of a vehicle upholstery member and opened to both sides when an air bag system is actuated, and two sheets of movable reinforcing panels which are fitted to a bracket disposed on the back side of the panel base in such a manner as openable to both sides via coupling members each having a loosening portion and fixed to the back sides of the corresponding door panels and wherein when an air bag starting to inflate after actuating the air bag system presses the movable reinforcing panels upward from the inside, a tear seam formed along the outer edge lines of the door panels ruptures to move the door panels upward from the panel base as the loosening portions of the respective coupling members are extended and deformed and subsequently a central tear seam formed along the center line between the adjoining door panels ruptures to open and displace the door panels toward a passenger""s chamber whereby to totally develop the air bag toward the passenger""s chamber, which structure is characterized in that:
each of the coupling members is formed semi-arcuately so that the loosening portion is capable of being linearly extended and deformed, and both the arcuate ends of the loosening portion are positioned close to the inner wall surface of the tubular portion of the bracket;
the length of each extended loosening portion is set to position the door panels so as to prevent the door panels from obstructing the overall development of the air bag and also to allow the door panels to be opened and displaced up to a position where the door panels are prevented from colliding with the surface of the panel base; and
when each of the door panels is opened after the air bag presses the movable reinforcing panels upward from the inside, the door panels are stopped from being opened and displaced at a point of time the loosening portions of the respective coupling members are completely extended whereby to prevent the door panels from colliding with the surface of the panel base.
According to still another aspect of the invention, there is provided an air bag door opening structure, wherein an air bag door comprises two sheets of door panels which are integrally formed with the panel base of a vehicle upholstery member and opened to both sides when an air bag system is actuated, and two sheets of movable reinforcing panels which are fitted to a bracket disposed on the back side of the panel base in such a manner as openable to both sides via coupling members slidably disposed for the bracket and fixed to the back sides of the corresponding door panels and wherein when an air bag starting to inflate after actuating the air bag system presses the movable reinforcing panels upward from the inside, a tear seam formed along the outer edge lines of the door panels ruptures to move the door panels upward from the panel base as the coupling members are slid and displaced and subsequently a central tear seam formed along the center line between the adjoining door panels ruptures to open and displace the door panels toward a passenger""s chamber whereby to totally develop the air bag toward the passenger""s chamber, which structure is characterized in that:
each of the coupling members is incorporated in the bracket by inserting a bar-like member through a slit extended along the sliding direction of the coupling member so that the bar-like member is allowed to slidably move from one end to the other end of the slit;
the length of each slit is set to position the door panels so as to prevent the door panels from obstructing the overall development of the air bag and also to allow the door panels to be opened and displaced up to a position where the door panels are prevented from colliding with the surface of the panel base; and
when each of the door panels is opened after the air bag presses the movable reinforcing panels upward from the inside, the door panels are stopped from being opened and displaced as the coupling members slide and as the other end of each slit is brought into contact with the bar-like member whereby to prevent the door panels from colliding with the surface of the panel base.